1. Field of the Invention
The present invention relates to metallic nanostructures, and more particularly, to layered structures comprising a dielectric material layer positioned between metallic layers and their use in metal enhanced emissions systems to enhance emissions from fluorophores, including intrinsic and extrinsic fluorophores; luminophores; bioluminescent species and/or chemiluminescent species.
2. Background of the Related Art
Fluorescence detection is an important tool in medical diagnostics high-throughput screening, microscopy and indeed biotechnology today.1-5 While fluorescence spectroscopy displays exquisites sensitivity,2, 6, 7 the detection limit is usually limited by the quantum yield of the fluorophore (label), the autofluorescence of the sample and the photostability of the fluorophores, which are fundamentally far-field fluorescence properties.8 In this regard, metallic nanostructures9-12 have been used to favorably modify the spectral properties of fluorophores and to alleviate some of their more classical photophysical far-field constraints.13-23 The use of fluorophore-metal interactions has been termed Metal-Enhanced Fluorescence (MEF) by Geddes.24 To date, MEF from plasmonic nanostructured materials such as Silver,25,26 Gold,27, Copper,28 Zinc,29 Chromium,30 Nickel,31 Tin,32 and Iron,33 have been observed. In this regard, silver island films (SIFs) have been popular substrates used for applications of MEF for fluorophores emitting in the visible wavelength region.
However, these studies have for the most part been focused on one SIF layer14, 34-36 and thus provide no ability to provide different layer sizes or components within such layers to provide tunable responses from the SIFs. Thus, it would advantageous to provide multiple layers of such metallic particles with a metallic oxide layer positioned therebetween to provide increased intensity of emissions and photostability.